Abstract
Twelve allozyme loci were examined in a complex of closely related diploid (2n = 18) members of the genus Chenopodium occurring in the western United States. These plants are generally treated taxonomically as belonging to C. atrovirens, C. desiccatum, C. hians, C. leptophyllum, and C. pratericola. Also included were populations referable to C. incognitum. The enzymes examined and the allelic designations are given as follows: leucine aminopeptidase, Lap; phosphoglucoisomerase, Pgi‐1, Pgi‐2; glutamate‐oxaloacetate transaminase, Got‐1, Got‐2, Got‐3; glutamate dehydrogenase, Gdh; phosphoglucomutase, Pgm‐1, Pgm‐2; malate dehydrogenase, Mdh‐1, Mdh‐2; and malic enzyme, Me. All populations were fixed for the same allele at Gdh, Pgi‐2, and Mdh‐1. Chenopodium hians was fixed for a unique allele at Got‐3 and contained two alleles at the Lap locus and two at Pgi‐1 which were not detected elsewhere. Chenopodium leptophyllum likewise has unique alleles at Lap and Pgi‐1. The other three taxa, C. atrovirens, C. desiccatum and C. pratericola, have alleles at Lap and Pgi‐1 which were not found in C. hians or C. leptophyllum. The former three species have the same alleles in highest frequency at all polymorphic loci except Me, where C. desiccatum is consistently separable from C. atrovirens and C. pratericola. Allozyme data are concordant with information from morphology, flavonoid chemistry and seed protein profiles in suggesting that: (1) Chenopodium hians and C. leptophyllum are best regarded as distinct species; (2) C. atrovirens and C. pratericola are very similar and perhaps should not be recognized at the specific level; (3) C. desiccatum appears most closely allied to C. pratericola; (4) plants referable to C. incognitum represent two biological entities, one the same as C. atrovirens, and the other conspecific with C. hians; (5) little genetic variation is detectable in any taxon of these weedy annuals; (6) interspecific hybridization is not a cause of taxonomic difficulties in these plants.
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